4.8.3 attr-get

The function attr-get gets the current attributes and color
pair of the window. Though we might not use this as often as the
above functions, this is useful in scanning areas of a screen. Say we
wanted to do some complex update on the screen and we are not sure
what attribute each character is associated with. Then this function
can be used with either attr-set! or attr-on! to produce the
desired effect.